1. Field of the Invention
Embodiments of the present disclosure generally relate to a method and apparatus for anti-islanding of distributed power generation systems.
2. Description of the Related Art
Solar panels have historically been deployed in mostly remote applications, such as remote cabins in the wilderness or satellites, where commercial power was not available. Due to the high cost of installation, solar panels were not an economical choice for generating power unless no other power options were available. However, the worldwide growth of energy demand is leading to a durable increase in energy cost. In addition, it is now well established that the fossil energy reserves currently being used to generate electricity are rapidly being depleted. These growing impediments to conventional commercial power generation make solar panels a more attractive option to pursue.
Solar panels, or photovoltaic (PV) modules, convert energy from sunlight received into direct current (DC). The PV modules cannot store the electrical energy they produce, so the energy must either be dispersed to an energy storage system, such as a battery or pumped hydroelectricity storage, or dispersed by a load. One option to use the energy produced is to employ inverters to convert the DC current into an alternating current (AC) and couple the AC current to the commercial power grid. The power produced by such a distributed generation (DG) system can then be sold to the commercial power company.
Under some conditions, a grid-connected DG system may become disconnected from the utility grid, resulting in a potentially dangerous condition known as “islanding”. During islanding, the utility cannot control voltage and frequency in the DG system island, creating the possibility of damage to customer equipment coupled to the island. Additionally, an island may create a hazard for utility line workers or the general public by causing a line to remain energized that is assumed to be disconnected from all energy sources. In order to mitigate the potential hazards of islanding, the IEEE standard 929-2000 requires inverters in a DG system detect the loss of the utility grid and shut down the inverter within two seconds. As such, all commercially available inverters, including each micro-inverter of a micro-inverter array, must be equipped with an inverter-based anti-islanding capability. Current techniques employed to meet such a standard require substantial power, thus reducing the efficiency of the inverter.
Therefore, there is a need in the art for a method and apparatus for fast detection of islanding in a grid-connected inverter.